Oscillation spiral coil and connection



E. F. NORTHRUP.

OSCILLATION SPIRAL COIL {\ND CONNECTION.

APPLICATION FILED JUNE 18. 19H.

Patented Feb. 10, 1920.

III, III! A witweoo UNITED STATES PATENT OFFICE.

EDWIN F. NOBTHBUP, OI PRINCETON, NEW JERSEY, ASSIGNOB TO THE AJAX METAL comm, OF PHILADELPHIA, PENNSYLVANIA,

VmA.

To all whom it may concern:

Be it known that I, EDWIN F. Noa'rnnur, a citizen of'the United States, residing at 30 street, Princeton, in the county of Mercer and State of New Jersey, have invented certain new and useful Oscillation Spiral Coils and Connections, of which the following is a specification.

The purpose of my invention is to concentrate the energy of an oscillation heating coil upon the resistor to be heated.

A further purpose is to provide an oscillation coil windin having a minimum voltage fall between t e resistor or its container and the adjacent parts of the coil.

A- further purpose is to so wind an oscillation coil as to bring the approximate center of'tihe coil, having most nearly the potential of the earth, closest to the object to be heated.

A further purpose is to reduce the difference in potential between windings of an oscillation coil and the object to be heated and the oscillation coil from these features.

A further purpose is to apply the heat to a non-conducting or poorly conducting object to be heated by inclosing the object within a resistor separate from a crucible or the resistor within the object and heating the resistor by induced currents.

A further purpose of my invention is to produce an electric furnace which- .takes a leading current, enabling me to use the lagging-current. usually available to ad-. vantage and to compensate bv positive reactance so as to secure unity power factor.

Further purposes relate to the processes or methods involved, as well as to other benefits which flow from the mechanism Specification of Letters Patent.

Patented Feb. '10, 1920.

Application filed .Tune 18, 1917. Serial No. 175,519.

whereby they may be performed, and will be found in the specification and in the cla1ms.

I have preferred to illustmte my in" ventlon by but a few of the forms in which it may practised, selecting therefor forms which, 1n use, have proved to be safe, prac-.

tical, eflicient and capable of heatin high temperature and which at t time well illustrate the principles invention.

to very e same of my A CORPORATION OF PENNSYIE Figure 1 is a vertical section of one form.

of my invention with diagrammatic connectlons showm one source of oscillatory current supply or it.

F g. 2 is a top plan view of the coil and crucible structure seen in Fig. 1.

Big. 3 is a. diagrammatic view showing two-phase connections for energizing two sets of coils similar to the set in Fig. 1.

Fig. 4 is a diagrammatic illustration showlng the application of the arrangement shown in Fig. 3 to another type of a helical oscillation heating coil. FlgS. 5, 6, 6 and 7 are sectional views showing several other means of applying my invention.

Fig. is a diagrammatic view showing clrcmt connections Fig. 9 is a diagrammatic view used in explanation of theory discussed herein.

Similar numerals of reference indicatelike parts.

In the use of oscillation currents for electric furnace-work the oscillation current has been passed through a coil of helical coil form surrounding the resistor, as dis.- closed and claimed inmy copending application for oscillation current method and apparatus, Serial No. 133,474, filed November 25, 1916.

The electric energy stored in the condenser, discharging through this coil, os-- cillates until the energy is finally dissipated in electric radiation, work and heat. The enormous rate of change of. the induction results in very rapid transfer of energy to ion " ing the circulation desired and has attained very high temperatures. However, for

some special uses such as the melting of latinum and other metals having a very high melting point, or in which so small a depth of material is to be treated that but few turns of the helical coil can conveniently be applied, it is desirable to attain a higher concentration of oscillatory current about the resistor than can conveniently be obtained by the helical coil form.

For this purpose I have invented a form using a pan-cake spiral which gives amuch higher concentration within the belt affected than-can be attained by the helical spiral and which, arranged in series in pairs connected at their inner ends, possess the additional advantage of having the points of highest potential farthest from the crucible or resistor.

The concentration of the field at the center of a pan-cakespiral coil will be appreciated from a brief discussion of the theory applying thereto.

The intensity of the field at the center of a circular coil of one turn carrying a current 5 is where? is the radius of the coil. Let the.

coil be wound with n turns to unit length measured along the radius, then the'field dueto these 'n. turns of average radius 1', is

, then v This gives, within a belt of very short vertical'height, substantially the same energy as would be distributed over the entire axial length of a helical coil having the same number of turns, greatly concentratin the heatmg effect and increasing the circu ation.

- commercial alternating current When high temperatures are required, the heat of the resistor, here illustrated as metal in.a crucible, reacts upon the coil and also causes ionization of the air immediately about the resistor affording a ready path of leakage from coil to the resistor or the crucible, where one is used, or even from one ortion of the coil to another. This is ob ectionable because of the danger of inury to workmen by reason of the high voltage leakage and'also because of the waste of energy which then does not pass through the entire coil. My pan-cake spiral form is practically unaffected by the ionization of the air about the resistor.

' I show several sets of circuit connections for my both in the number of phases of current utilized and in the location of the condenser and the discharge gap. These are placed in a se arate circu1t from that including the 0011 in Fig. 1 though the two circuits are inductively connected. They are located in the same circuit witlrthe coils in which the oscillatory current is supplied, as

the variety of circuits suitable for the purpose is recognized by -me to be very great. I In Figs. 1 and 2 I showthe crucible 10 as surrounded by an oscillation coil 11 intended for single phase use, comprising two concentric, superimposed, oppositely wound pan-cake spirals 12, 13, joined at their inner ends and inductively disposed as at 14 and connected with the supply circu t at their respective outer ends 15, 16, so that the oscillation current used enters one coil at its circumference and flows in spirals of decreasing radius toward its inner end and thence flows out in spirals of increasing radius to the extremity of the other coil.

In all of these coils I find lamination desirable in the reduction of losses due to eddy currents and may use laminated strips or wires here.

The energy furnished is derived from any circuit, represented generally by the single phase primary circuit A A I have successfully used 220 volt current of cycles frequency. With other than the desired voltage,.I transform the current at 17 to charge condenser 18, which, at the required voltage, could charges through any discharge gap 19. I

have secured thebest results with a voltage.- of from 8,000 to 10,000 and a high voltage double discharge gap across from 'a 8011(1 electrode to mercury-21 at one gap and moons:

across from a second pool of mercury 22 'to a solid electrode '23 at the other, in one direction oftravel and across similar gaps in the opposite direction. The mercury electrodes are electrically connected at 24.

which t e an-cake s iral coils are applied- Serial No. 175 518 filed June ll through one winding 25 of a mutual in uctance 26-whose The high negative electrode resistance of mercury is thus utilized m both directions of current travel. Thisf'is an excellent type of gap but, per 86, is not claimed in my present application, being embodied in a separate application for patent for discharge 18, 191

e condenser dischar other winding 27 is in series with and supplies the pancake spiral coil 11..

For the mason that spirals are at maximum and opposite potential asindicated and their inner connected ends are', as a result, at substant ally zero potential, the pan-cake coils of the pair are inductively wound as appears from i 2. I Thou h the character of the resistor to does not a set their t eory of operatlon as coils, the prospect of immediate and highl desirable practical use in. melting meta 3 having high melting points has led me to illustrate my invention in the figures as.-

applied to crucibles 10, 10 ,10 10" and their contents 28.

Obviously the number of pairsof an-' cake spirals used,.whether with single p iase or multi-pha'se supply, will depend upon the height of the crucible content, the desired depth and spacing of the ind1v1dual spiral coils and other a treated, special conditions met, etc., such as determine the design in individual cases.

In 3 the oscillation coil 11 in Fig 1 has been duplicated at 11', at another point along the height of the crucible and is used with any of a large variety of twophase connections.- v

The two phases A, A,, B, B of the primarycurrent source are shown as provided with-Adjustable inductances 29, 29 and as transformed at 30, 30' to chargewo'ndensers 18, 18.-l The condensers discharge through discharge gaps here illustrated as plural gaps passing from a solid electrode to mercu and from the mercury to asolid elect e in each base and'in each direction of 4 impulse trave These gaps are shown as contained in a single pct 19., ha three solid electrodes 31, 32 and 33 of whic 32' is shown as connected to the neutral point.

These discgg rge gaps utilize a common mercul nii tbhminal of each of the two spiral coil the outer ends of the 'ctors of material,

' the range of suitab furnace pairs is as at 16,16 with one of the condensers and the other terminal of each, as 15, 1 is connected with the. commonsolid el node.

CObviousl the two pairs of pan-cake '10 -s 'irals cou d be arranged separately as in ig..4, "or in multiple using s' le phase supply; and also the same two-p see-0on motions can be used. with other spiral coils of which 'one helical oscillatory heating co' illustration is given Fig. 4. Both spiral forms offer some advantage with multiphase connection, particularly as'the commercial alternating current sulppl in many cases is multi-phase and sing e p are penalized for unbalancmg the multiplhase circuits. .With the connections SlIOWli, t e

uiredcurrent is drawn eqi1ally from both p uses and no unbalancing takes place.

I believe that I am the first to produce an electric furnace circuit which takes a lead' current-. e.- in which the secondaries o the transformers or the rimary -curreiit supply leads into aninitia negative reactancev his condition in my furnacemakes it possible to secure unity power factor by means of the adjustable positive reactances; 'and those can be placed either inthe primary or the secondary circuit. Most commercial circuits have a lagging current. The .user can '95 sometimes purchase powerniore cheaply if supplying a load that has an initial leading current.

f it be desired to connect-the coil in Fig.

4 in such a circuitas that in Fig. 3, the

terminals 15 will correspond with terminals 15, 15" of Fig. 3 and terminals 16, 16 will i correspond with terminals 16, 16'.

Because of the extreme difiicultyin melt- I ing platinum in an electric furnace, I have. illustrated one construction in Fi 5 intended especially for this use. Th1s metal is melted, commercially, in small quantities and most desirably in a vacuum. The latinum 28' to be melted is therefore inc osed' within a quartz bell jar 31 resting upon a as the tem rature to be attained reduces. 1 25 ,Whatever t e material used for this auxiliary or su plemental resistor, it may be used a to assist 1n the heating of the platinum or other material treated. When treating substances which are non-conductors of elec- 1&0

880 users 80 sistor 36, it ma three pan-cake coils connected at their inner ends at 14 and'having their outer terminals 15 15 15 adapted for three phase star current supply, which may be furnished by such connections, for example, as in Fig. 8.

In Fig. 6 I have shown the positions of the material being treated and the auxiliary or, main resistor as reversed with res ect to the arrangement in Fig. 5. The cruel le 10 is placed within a crucible 10 leaving a s ace 35 between them, within which space t e material to be treated is inserted. The

auxiliar or main resistor, as the case may be, is p aced within the inner crucible and may be in the form of grains'or small pieces of tungsten, molybdenum or even iron. I have successfully used steel nails for this purpose where the temperature to be secured was not too high.

Whatever the material composing the reevidently be disposed in various ways with respect to the material which is to be heat-treated.

In Fig. 6 I have shown a molybdenum cylinder 37 as surrounding the crucible 1 0. The helical spiral form of winding is shown with two-phase connections.

In Fig. 7 the truncated conical wind-' mgs partake in part of the nature of each of the two types of spiral previously discussed, in that the successive turns continuously vary in radius at the same time that they pro ress axially along the resistor. A

part of t e benefit of each of the other two windings isthus secured. The cross section of the coil 11 is here circular, ermittin lamination as with the other con uctors an with the same advantage.

In Fi 8 connections are shown for one form 0 three phase star winding. The secondary of a three hase star transformer is shown at 17 and is connected with discharge gaps 19 19 and 19. Each of these gaps is of my preferred double-gap form'of solid-to-mercury and mercury-to-solid type, the second solid electrodes in all three gaps being connected together so that these double y ga s dischar e in series in each case.

hree con ensers 18, 18, 18 are charged from the transformer secondary in series of two and discharge in series through two furnace coils and two double-ga discharge gaps'in each case in the illustration. Three star connected furnace coils 38, 38, 38, are shown and any of the forms of winding of the coils may be used. I

It will be seen that all of the forms ofmy invention permit maintenance of vacuum conducting investigation in a simple case.

conditions or any desired pressure of gas or gases or liquid or mixture thereof while the material treated is subjected to the heating effects of my coils, but that a greater intensity of induction in the resistor can be obtained with thepan-cake spiral form. The pressures of the atmos here of treatment may be above or be ow normal air pressure.

It will also be evident that I can obtain all the advantage of the use of an electrically crucible while actually. holding the material treated in a crucible of nonconducting material for heat-treatment of a non-conductor ofelectricity; and that independently of the character of crucible desired, I can obtain the benefit of a highly refractory conductor to improve the heating effect of an oscillation coil upon an electrically conducting resistor having a high melting point. p

In all of the uses of my invention it is desirable to apply the induction at a maximum rate of transfer of ener between the oscillation heating coil and t e resistor to be treated. I have therefore studied the conditions determining the ohmic resistance which the resistor should have for maximum rate of transfer and give the result of my 'Referring to the diagram in Fig. 9, let T be a transformer su plying current to charge condenser C throug resistance R and one of mutual inductance coils having inductance L Let L be the inductance of the other of these coils, S the resistance to be determined for the resistor and N the frequency of the. alternating current supplied. Then s-zm-L, and N= -Vali1e,'of S for maximum rate of energy-transfer to resistor circuit.

With the pancake spiral form I obtain a number of advanta 7 not be secured to t e same extent by any other form of coil One'of its chief advantages for oscillatory currents is its freedom from leakage and break-down at the arts nearest to the resistor where the big temperatures attained have ionized the air and the danger of leakage or breakdown is atest with other forms of coil. Bein mi way between the outer extremities of t e pancake coils, the inner turns are substantially at zero potential. I may furthermore ground the crucible or resistor as indicatedm some of the figures, giving additional security to the workmen.

All the points of high potential are distant s which I believe can-' volume of resistor making possible alarger number of turns r 2. A hollow increase 0 'for a given diameter and axial length than could otherwise be used.

"In each pair of s irals any desired rate of verti spacing between turns of correspondingly increasing radii and gotential difi'erence may be obtained by dou le cone-frustumconstruction. This will be true as shown in the pairs 12, 13' in Fig. 7; and palrs of such pairs may be joined as there shown, using twohase supply with the neutral at 15 and t e phase terminal connections at '16, .16.

As a result of .the advantages set out above, .my invention has great utility in stud g the melting points and pro aerties at high temperatures of various meta s,'re-

fractories and refractory oxids under spe-" cial conditions as to pressure and atmosphere, the making of fine glass and enamel, which can be done readily within an iron sagger, the testing of materials to determinetherr gaseous contents and preserve the residuums unchanged except for the removal of the gas, and a great man other uses, too numerous to mention but w 'ch will occur to those skilled in the various arts in view of my disclosures herein.

Having what Ijc aim as new and desire to secure .by Letters Patent is:.

H '1. A hollow pancake heating coil adapted to stand a high temperature and having the interior endof the coil spaced much farther from the center thereof than the spacing of adjacent turns of-the coil from each other.

ancake heating coil and a furnace inclosefthereb 3. Two superimp connected ancake heatin coils connected other at t eir inner en s, a furnace crucib e within .the coils and a source of electrical'energy applied to the outer ends of the coils.

4. A hollow pancake heating coil continuously varying in diameter and having the interior end of the coil spaced much farther from the center thereof than the spacing of adjacent turns of the coil from each other.

5. Two superimposed connected air-insulated pancake heatin coils havin the interior ends of the coi s\spaced fart er from the center thereof-than adjacent turns of it each coil are spaced from each other.

. passin necti 6. Two su rimposed air-insulated inductively-woun hollow heating coils connected at their inner ends and ha the interior ends of the coils spaced fa er from the center thereof than adjacent turns of each coil are spaced from each other.

7. Two hollow cake heating coils, eleccoils minals located radially at a considerable distan e from some of its turns in combination with a source of high frequency current supply therefor.

11. Two pancake spiral heating coils in superimposed position having the inner ends of the coils s aced much farther from the centers there or than the spacing adjacent turns of each coil from each other and means for paming electric current through both coils from the same source.

12. A pancake heating coil, means for oscillatin electric current therethroug and a resistor at the center of the coil receiving the induction therefrom.

l 13. A orluclilble and a hollow oscillation; leatin coi t erea out comprising a pair '0 spirals connected in proximity to their innor ends and progressively in diariieter toward theirl' terfiinals. l

'1 pair 0 spira coi progressive increasing in diameter and connected at heir inner ends, a crucible within the coils and a elecsource of oscillation current discharge oonwith the terminals of the coils.

15. 11 an electrical furnace, an alternating electric circuit, a mutual inductance coil, a condenser and 'a discharge ga arran in series and together in series wit one wmdin' of said mutual inductance coil, and an osci lation heating coil in serieswith the other winding of said mutual inductance coil.

16. In an electric furnace, an alternating current transformer, a condenser charged by the secondary of said transformer, a mutual inductance, one winding of which is in series with said charging circuit, a discharge gap thrown across the condenser and an oscillation heating coil in series with the other winding of said mutual inductance.

17. In an electric furnace, a mutual inductance, a condenser arranged to discharge through one winding of said mutual inductance, charging means for said condenser, a discharge gap adapted tOdischarge said condenser through said windlng, and an ostual inductance, means for impressing an oscillatory current upon the terminals of one winding thereof and a heating coil in circuit with the other winding thereof. v 20. In an oscillation coil furnace, a mutual inductance, means for supplying an oscillating current to one winding thereof and.

a heating means in circu'itwith the other winding thereof.

21. A heating coil and oscillatory inductive means for supplying current to the coil.

22. In an electric furnace, a pair of crucibles providing two resistor spaces, one within the inner crucible and the other be tween the crucibles, in combination with a conducting refractory in one of the spaces and'oscillation means for inducing electric current flow in the refractory.

23. In an electric furnace, a pairof crucibles providing two resistor spaces, one within-the inner crucible and the other between'the crucibles, in combination with a conducting refractory in one of the spaces.

24. In an electric furnace, a pair of nested crucibles roviding a space between the crucibles. and? a space within the inner crucible in combination with an auxiliary resistor in one of the spaces adapted to assist in the heatin or treating of a resistor in the other of sai spaces and oscillation means for inducingelectric current flow in the refractory.

25. In an electric furnace, a pair of nested crucibles roviding a space between the crucibles an 1 a space within the inner crucible,

in combination with an auxiliary resistor in one of the spaces adapted to assist in the heating or treating of a resistorin the other of said spaces.

26: In an electric furnace, an oscillation coil,-a crucible therein adapted to hold' a material tobe heated or heat-treated and a resistor surrounding the crucible and adapted to assist in heating the material in thecrucible. 27. The method of applying oscillation currents to the'heating of resistors which consistsin applying the highest potential of said oscillation currents at a distance from the [resistor and causing it to circulate about the resistor at distances becoming less as. the tential lowers.'-

- 28.. he method of applying oscillation currents'to the heating of resistors which consists in, applying the highestpotential of said oscillation currents at a distance from consists in applying t e highest potentials sists in applying terminals at'a distance from the resistor of the resistor and causing it to circulate about the resistor at distances becoming less as the potential lowers and maintaining approximately the potential of the earth at the point of closest approach to the resistor.

29. The method ofapplying. oscillation currents tothe heatin of a resistor which of said oscillation currents at the greatest distances from the resistor to be heated and causing the currents to circulate about the resistor at decreasing radial distances as the resistor is approached.

- 30. The method of heating a resistor by an oscillation current circulating about the resistor in inductive relation thereto, which consists in reversely directing theoseillation current between the two terminals in different planes, approaching and receding from the resistor as the current circulates about it and forming a connection between the two paths of cur ent flow in proximitytothe resistor.

31. The method of heating a, resistor to high temperature by oscillation currents which consists in circulating oscillation cur: rent about, it, maintaining the highest potential of oscillation current at the points of lowest temperature and reducing the potential of the oscillation current as points of higher temperature are approached.

32. In the method of heating a resistor to a very high temperature, the step which con; an oscillation current to separate windings which encircle and approach the resistor and joining the windings at the point of nearest approach to the re sistor and highest temperature.

33. The method of avoiding the injurious effects of air ionization in proximity to a resistor of very high temperature in oscillation coil heating thereof which consists in placing a part of the coil having the ap proximate of the earth potential in the position of" highest temperature and in disposing the parts of the coil of higher potential at increasing distances from the resistor.

34. The method of heatin by oscillation currents which consists in orming an 05- cillation current in one circuit, in transforming said current into a second circuit and utilizing the oscillation current for heatin purposes in said second circuit.

35. he method of utilizing oscillatory currents for heating uses, which consists in charging and discharging acondenser through a' difierent circuit from that in which theheat utilizin I F. NORTHRUP.

means is included and in inductivegcou ing the two circuits. 

